How build angle and post-processing impact roughness and corrosion of additively manufactured 316L stainless steel

Additively manufactured austenitic stainless steels exhibit numerous microstructural and morphological differences compared to their wrought counterparts that will influence the metals corrosion resistance. The characteristic as-printed surface roughness of powder bed fusion (PBF) stainless steel parts is one of these morphological differences that increases the parts susceptibility to localized corrosion. This study experimentally determines the average surface roughness and breakdown potential (E b ) for PBF 316L in 6 surface finished states: as-printed, ground with SiC paper, tumble polished in abrasive media, electro-polished, chemically passivated, and the application of a contour/re-melt scan strategy. In general, a smaller average surface roughness led to a larger E b . The smoothest surface treatments, ground and electro-polished conditions, led to E b near the materials limit (~+1.0 V Ag/AgCl ) while all other surface treatments exhibited significantly lower E b (~+0.3 V Ag/AgCl ) The build angle was also shown to impact surface roughness, where surfaces at high angles from the build direction resulted in larger roughness values, hence lower E b .